The following configuration is known as a relay unit (relay circuit) that has the function of switching between current flow and no current flow of a load using relays.
That is, the relay unit includes an insulating member for insulating and separating a load power supply for operating a load from a device power supply, which is different from this load power supply. Note that the device power supply functions as a power supply for operating mainly a microcomputer (microcontroller) of the relay unit and the like. Examples of the relay unit including the insulating member are disclosed in JP H5-55435U and EP 1202313A.
The specifications of JP 5-55435U (Jul. 23, 1993) and EP 1202313B (May 2, 2002) are examples of background art.
When an insulation failure (such as a short circuit) of the insulating member occurs, there is the risk that the following defects occur: A high voltage may be applied to the relay unit from the load power supply, causing a fault of the relay unit, a voltage may be applied to the load from the device power supply, causing a malfunction of the load, and the like.
Note that as means for preventing various defects that are caused by the insulation failure, it is conceivable to increase the number of insulating members. However, even when the number of insulating members is increased, insulation failures may occur in, for example, all the insulating members due to a common reason. Accordingly, even by increasing the number of the insulating members, it is difficult to sufficiently suppress various defects that are caused by the insulation failures.
The present invention was made in view of the above-described problem, and an objective thereof is to provide a relay unit that can sufficiently suppress defects that are caused by insulation failures of insulating members for insulating and separating a load power supply from a device power supply, and a method for controlling a relay circuit.